1 Scope
This document describes a procedure for the calculation of the tooth flank fracture
load capacity of cylindrical spur and helical gears with external teeth.
It is not intended to be used as a rating method in the design and certification process
of a gearbox.
The formulae specified are applicable for driving as well as for driven cylindrical
gears while the tooth profiles are in accordance with the basic rack specified in
ISO 53. They can also be used for teeth conjugate to other racks where the actual transverse
contact ratio is less than εα = 2,5. The procedure was validated for case carburized[15] gears and the formulae of this document are only applicable to case carburized gears
with specifications inside the following limits:
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— Hertzian stress: 500 N/mm2 ≤ pH ≤ 3 000 N/mm2;
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— Normal radius of relative curvature: 5 mm ≤ ρred ≤ 150 mm;
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— Case hardening depth at 550 HV in finished condition: 0,3 mm ≤ CHD ≤ 4,5 mm.
This document is not applicable for the assessment of types of gear tooth damage other
than tooth flank fracture.